Torque indicating tool



N. c. COLLINS TORQUE INDIGA'IING TOOL May 28, 1946.

Filed May 19, 1945 INVENTOR. NORMAN 0.

COLLINS ATTORNEY.

Patented May 28, 1946 2,400,978 TORQUE INDICATING TOOL Norman 0.Collins, San Diego, Calif., assignor to Solar Aircraft Company, SanDiego, Calif, a

corporation of California Application May 19, 1945, Serial No. 594,621 4Claims. (Cl. 73 139 Thi invention relates to tools for applying a knowntorque to nuts, screws, etc., and is particularly useful in a tool ofthe screw-driver type in which the handle extends cc-axially with thescrew or nut being turned. 7

An object of the invention is to provide a particularly simple, reliableand inexpensive torque indicating tool that is relatively accurate andcan be easily adjusted for purpose of calibration.

Other more specific objects and features of the invention will appearfrom the detailed description to follow of a specific embodiment of theinvention a illustrated in the drawing.

Briefly, the present invention comprises a hollow handle having a shaftjournaled in its forward end, which shaft carries a screw-driver bit ora wrench on its forward end, the shaft being connected to the handle bya torsion spring extending between the rear end of the shaft and therear end of the handleso that when torque is applied to the handle, thehandle yields with respect to the bit or tool to an extent proportionalto the torque that is applied. An indication of the torque is obtainedby providing a dial on the forward end of the handle and a pointerconnected to the bit or wrench, so that the exact relative movementbetween the handle and the bit is indicated by the extent of movement ofthe pointer with respect to the dial.

Tools of this general type are not broadly new, but the present toolincorporates details of construction that improve the efficiency andreliability of the tool, make it easy and inexpensive to manufacture,and provide for ready adjustment for calibration purposes. These detailswill become apparent from the following description with reference tothe drawing, in which:

Fig. l is a longitudinal section through a tool in accordance with theinvention;

Fig. 2 is a cross-section taken in the plane II-II of Fig. 1;

Fig. 3 is a cross-section taken in the plane III1'II of Fig. 1; and

Fig. 4 is an end view taken in the plane IV-IV of Fig. 1.

Referring first to Fig. 1, the tool therein disclosed comprises a hollowhandle consisting of a rear section l and a forward section H which areinterconnected by screw threads. Thus the rear handle section II) is oflarger diameter than the front handle section H and is internallythreaded, as indicated at 12, to engage external threads 13 on the frontsection. The two sections can be locked together ina desired position ofadjustment by means of a lock nut l4.

. of the handle section H.

The front handle section II rotatably sup ports a shaft l5 which extendsout of both ends There is secured to the front end of the haft [5 aguard member I6 having on its outer end an annular flange I! whichsurrounds a screw-driver bit l8 formed integrally with the shaft E5. Theguard Hi can be locked in any desired position of rotation on the shaft15 by aset screw [9 which engages a groove 20 in the shaftlE. A shoulder2| is formed integrally on the shaft l5 between the annular groove 2!]and the bit [3 for transmitting end thrust from the bit 58 to the guardIt. The rear end of the guard l6 bears against the front end of thefront handle section II to prevent rearward movement of the shaft 5 withrespect to the handle.

Secured to the guard It, as welding 22, is a pointer 23 which cooperateswith a dial 24 secured to the forward end of the front handle section HAs best shown in Fig. 3, the rear face of the dial 24 bears graduations25 indicating the position of the pointer 23 with respect to the dial24.

The rear end of the shaft I 5 is connected to the front end of a flatleaf spring 26 which extends longitudinally within the rear handlesection I0. The forward end of the spring 26 is slidably fitted in aslot 21' in the rear end of the shaft I5. A collar 28 is press-fitted onthe rear end of the shaft l5 surrounding the slot 21 for performing thetwo functions of: (1) preventing a spreading of the slotted rear endportion of the shaft in response to torque between the shaft and thespring 26; and (2) to act as a thrust bearing on the rear end of theshaft l5 to prevent forwardmovement of the shaft within the front handlesection II.

The rear end of the spring 26 is adjustably connected to the rear end ofthe rear handle section II]. Thus the rear end of the spring extendsinto a slot 29 in a bushing 30 which is slidably fitted in an aperture3| in the rear end of the rear handle section H).

The slot 29 is dimensioned to freely slidably receive the leaf spring 26to permit longitudinal adjustment of the bushing 30 with respect to boththe rear handle section I 0 and the leaf spring 26. When the bushing hasbeen positioned a desired longitudinal location, it is securely lockedin that position by tightening a set screw 32 which is threaded into thewall of the rear handle section ID. The bushing 30 is provided with oneflat side 34 parallel to the slot 29 and the lock screw 32 bears againstthis fiat side,.thereby preventing rotation of the bushing with respectto the handle. When the lock screw 32 is tightened, it not only looksthe bushing 30 against either rotational or longitudinal movement withrespect to the handle, but it also clamps the rear end of the leafspring firmly in the slot 29 in the bushing.

The particular tool disclosed in the drawing is intended to measuretorque applied in either direction, and to this end the pointer 23 isnormally positioned at a mid or zero point on the scale 25. Applicationof torque in either direction between the handle and the bit l8angularly displaces the handle with respect to the bit by an amountdepending upon the torque applied and the stiffness of the spring 26.The scale 25 may be calibrated to read the torque in any well knownunits, such as inch-pounds, inch-ounces, foot-pounds, etc.

The instrument can be calibrated in either one of two ways, both ofwhich involve changing the effective length of the leaf spring 26between the inner end of the bushing 36 and the rear end of the shaftl5. If the elfeotive length of the spring 26 is reduced, its stillnessis increased and viceversa.

One methodof adjustment is to loosen the set screw 32 and slide thebushing 30 either forwardly thereby shortening the effective length ofthe spring 26, or rearwarly, to lengthen it, and then re-tighten thelock screw 32 to hold the bushing in the new position of adjustment.

Another method is to change the relative positions of the handlesections In and H by rela tively rotating them. Obviously, this is doneby first loosening the lock nut l4 and then rotating the rear handlesection l relative to the front handle section I 1. Obviously the handleI6 must be rotated through one or more revolutions dur- 7 ing eachadjustment in order to normally dispose the pointer 23 opposite the zeromark on the scale 25. This method is, therefore, best suited for coarseajustments of the calibration. A fine adjustment can then be had byshifting the bushing 30.

The tool is very easily assembled from its component parts as follows:first, the guard I6 is slipped into place on the shaft over the rear endof the shaft until the collar abuts against the shoulder 2 I, whereuponthe set screw I9 is screwed in until it engages in the groove 20 toretain the guard 16 in place. The shaft I5 is then inserted into thefront handle section II, after which the front end of serted in the slot21. Next the collar 28 is pressed onto the rear end of the shaft l5,thereby completing the assembly of the shaft l5 and its associatedelements with respect to the front handle section II,

Prior to the assembly of the shaft IS in the front handle section I l,the dial 24'is pressed onto the front end of the handle section II.Assembly is then completed by slipping the bushing 30 onto the rear endof the leaf spring 26 and therel0 onto after screwing the rear handlesection the front handle section I I.

A pair of stop pins 31 and 38. may be provided on the dial 2-4,projecting from the forward face of the dial for contacting the pointer23 and limiting movement of the pointer. This enables the application oftorques greater than those the tool is adapted to measure, withoutdamaging the spring 26.

It is to be understood that the flange l1 surrounding the screw-driverbit l8 may be elimithe leaf spring 26 is inhollow handle; a shaftrotatably supported in the beyond; work-engaging means on forward end ofsaid handle and projecting therethe forward end of said shaft forengaging a rotatable workpiece coaxial with said shaft; cooperatingpointer and dial elements, one secured to the forward end of said handleand the other secured to the projecting portion of said shaft forindicating an angular displacement between said elements; a torsionspring extending longitudinally within said handle and connected at itsforward end to the rear end of said shaft for rotation therewith; acoupling element adjustably longitudinally slidable with respect to therear end of said torsion spring and the rear end of said handle; and asingle locking means for locking said couplin element rigidly to bothsaid handle and said torsion spring.

2. A tool as described in claim 1 in which said coupling elementcomprises a slotted bushing slidably fitted in the rear end of saidhandle and said torsion spring comprises a fiat spring, the slot in saidbushing being dimensioned to slidably receive the rear end of said fiatspring, and a set screw in said handle adapted to bear against saidbushing and compress it into tight engagement with said spring.

' forward end of said handle and projecting therebeyond; work-engagingmeans on the forward end of said shaft for engaging a rotatableworkpiece coaxial with said shaft; cooperating pointer and dialelements, one secured to the forward end of said handle and the othersecured to the projecting portion of said shaft for indicating anangular displacement between said elements; a torsion spring extendinglongitudinally within said handle and connected at its forward end tothe rear end of said shaft for rotation therewith; means for connectingthe rear end of said torsion spring to said handle for rotationtherewith, said handle comprising a front section in which said shaft isjournaled' and a rear section of larger diameter to which the rear endof said torsion spring is connected, said sections being adjustablyinterconnected by external screw threads on said front section engaginginternal screw threads in said rear section; and means for looking saidsections against relative movement.

4. A tool of the type described comprising: a hollow handle; a shaftrotatably supported in the forward end of said handle and projectingtherebeyond; work-engaging means on the forward end of said shaft forengaging a rotatable workpiece coaxial with said shaft; cooperatingpointer and dial elements, one secured to the forward end of said handleand the other secured to the projecting portion of said shaft forindicating an angular displacement between said elements; a torsionspring extending longitudinally within said handle and connected at itsforward end to the rear end of said shaft for rotation therewith; meansfor connecting the rear end of said torsion ably interconnected witheach other; stop means on the front end of said shaft bearing againstthe front end of said front section; and a collar press-fitted on therear end of said shaft and bearing against the rear end of said frontsection for supporting said shaft against longitudinal 5 movement insaid front section.

NORMAN C. COLLINS.

